Nickel manganese cobalt composite hydroxide, method for producing nickel manganese cobalt composite hydroxide, lithium nickel manganese cobalt composite oxide, and lithium ion secondary battery

ABSTRACT

A nickel manganese cobalt composite hydroxide, which is a precursor of a positive electrode active material, and which is composed of secondary particles to which primary particles containing a nickel, a manganese, and a cobalt are aggregated, or composed of the primary particles and the secondary particles, wherein a sodium content contained in the nickel manganese cobalt composite hydroxide is less than 0.0005% by mass. Also, a ratio of an average particle size of a lithium nickel manganese cobalt composite oxide divided by an average particle size of the nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of the lithium nickel manganese cobalt composite oxide selected randomly by a scanning electron microscope, a number that an aggregation of secondary particles is observed is 5% or less with respect to a total number of observed secondary particles.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a nickel manganese cobalt compositehydroxide, which is a precursor of a positive electrode active material,and which is composed of secondary particles to which primary particlescontaining a nickel, a manganese, and a cobalt are aggregated, orcomposed of the primary particles and the secondary particles, a methodfor producing the nickel manganese cobalt composite hydroxide, a lithiumnickel manganese cobalt composite oxide, and a lithium ion secondarybattery. This application is based upon and claims the benefit ofpriority from International Patent Application No. PCT/JP2019/001797filed on Jan. 22, 2019, and International Patent Application No.PCT/JP2019/016269 filed on Apr. 16, 2019.

Description of Related Art

In recent years, needs for a development of high-power secondarybatteries as batteries for electric cars and hybrid cars are expanding,including compact and lightweight non-aqueous electrolyte secondarybatteries having a high energy density, due to the widespread use ofportable electronic devices such as smart phones, tablet terminals andnotebook computers.

As a secondary battery which can cope with such needs, there is alithium ion secondary battery. A lithium ion secondary battery includesa negative electrode, a positive electrode, and an electrolyte solution,and uses materials that can de-insert and insert lithium as a negativeelectrode active material and a positive electrode active material.Lithium ion secondary batteries are now actively being researched anddeveloped. Particularly, lithium ion secondary batteries using a layeredor spinel-type lithium metal composite oxide as a positive electrodematerial can provide a 4 V-class high voltage, and are thereforepractically used as batteries having a high energy density.

Among them, a lithium nickel manganese cobalt composite oxide isattracting an attention as a material which can obtain high output withlow resistance and has excellent cycle characteristic of batterycapacity, and in recent years, it is considered to be important as apower supply for cars, as it is suitable for a power supply for electriccars and hybrid cars, in which a vehicle loading space is restricted.Generally, a lithium nickel manganese cobalt composite oxide is producedby a process to mix and fire a nickel manganese cobalt compositehydroxide, which is a precursor, with a lithium compound.

In this nickel manganese cobalt composite hydroxide, impurities such asa sulfate radical, a chloride radical, a sodium and the like, derivedfrom a medicament or raw materials used in a production process, areincluded. In a process to mix and fire a nickel manganese cobaltcomposite hydroxide with a lithium compound, these impuritiesdeteriorate a reaction with a lithium by inducing a side reaction andthe like, so a crystallinity of a lithium nickel manganese cobaltcomposite oxide in a layered structure will be decreased.

In a lithium nickel manganese cobalt composite oxide with acrystallinity decreased by an effect of impurities, a battery capacitywill be decreased as a diffusion of a lithium in a solid phase isinhibited, when composing a battery as a positive electrode activematerial. Also, these impurities almost do not contribute to charge anddischarge reactions, so in a structure of a battery, for an amountcorresponding to an irreversible capacity of a positive electrodematerial, a negative electrode material must be used in a batteryexcessively. As a result, a capacity per volume or per weight as anentire battery will be decreased, and an excessive lithium will beaccumulated at a negative electrode as an irreversible capacity, so itwill be a problem also from a safety aspect.

Further, a potassium, a calcium, a magnesium and the like, including asodium dissolve to a lithium site, so particles of a lithium nickelmanganese cobalt composite oxide tend to aggregate by sintering, and ina lithium ion secondary battery produced by using this lithium nickelmanganese cobalt composite oxide, a reactivity will be deteriorated, andan output characteristic and a battery capacity will be decreased.

As impurities, there are a sulfate radical, a chloride radical, a sodiumand the like, and technologies for removing these impurities have beendisclosed so far.

For example, in a patent literature 1, it is disclosed to decrease asulfate radical or a chloride radical by performing a crystallizationprocess for obtaining a niobium-containing transition metal compositehydroxide, and by washing the obtained niobium-containing transitionmetal composite hydroxide with a carbonate aqueous solution such as apotassium carbonate, a sodium carbonate, and an ammonium carbonate.

Also, in a patent literature 2, it is disclosed to decrease impuritiessuch as a sulfate radical, a chloride radical, and a carbonate radicalby making an alkaline solution to be used for adjustment of pH into amixed solution of an alkali metal hydroxide and a carbonate in a processfor producing a nickel manganese cobalt composite hydroxide from acrystallization reaction.

Also, in a patent literature 3 and a patent literature 4, it isdisclosed to decrease a sulfate radical or a chloride radical and sodiumby washing nickel manganese composite hydroxide particles or nickelcomposite hydroxide particles having a void structure inside theparticles obtained in the crystallization process by a carbonate aqueoussolution such as a potassium carbonate, a sodium carbonate, a potassiumhydrogen carbonate, and a sodium hydrogen carbonate.

Also, in a patent literature 5, it is disclosed to use a nickel-cobalt-Melement-containing composite compound with low content of impuritiessuch as a sulfate radical, a chloride radical, sodium, and iron, bypyrolyzing a nickel ammine complex and a cobalt ammine complex byheating the nickel-cobalt-M element-containing aqueous solution oraqueous dispersion obtained by mixing the nickel ammine complex, thecobalt ammine complex and M element source.

-   Patent Literature 1: JP 2015-122269 A-   Patent Literature 2: JP 2016-117625 A-   Patent Literature 3: WO2015/146598-   Patent Literature 4: JP 2015-191848 A-   Patent Literature 5: WO2012/020768

SUMMARY OF THE INVENTION

However, regarding the patent literatures 1 and 2, it is not disclosedabout a removal of sodium at all. In addition, regarding the patentliterature 3 and 4, a reduction of sodium is insufficient as 0.001% to0.015% by mass of sodium still remains, even in a precursor of a solidlevel with a low void ratio of about 3%. Further, regarding the patentliterature 5, it is questioned that a battery characteristic will besufficient when used as a positive electrode active material, from apoint of view of a specific surface area, a particle size distribution,and a spherical shape of particles, as a nickel-cobalt-Melement-containing composite compound is obtained by a pyrolysis. Inaddition, a removal of impurities, a further improvement of a batterycharacteristic, and an inhibition of an aggregation by sintering areexpected.

Here, a purpose of the present invention is to provide a nickelmanganese cobalt composite hydroxide, which is a precursor of a positiveelectrode active material of a lithium ion secondary battery capable ofimproving a battery characteristic, and also, capable of surelydecreasing a sodium content especially, among impurities which almost donot contribute to charge and discharge reactions, and a method forproducing the nickel manganese cobalt composite hydroxide. In addition,a purpose of the present invention is to provide a lithium nickelmanganese cobalt composite oxide, which is a positive electrode activematerial, in which an aggregation by sintering is inhibited, and whichis produced by using the nickel manganese cobalt composite hydroxide, inwhich a sodium content is surely decreased, and a lithium ion secondarybattery.

A nickel manganese cobalt composite hydroxide relating to one embodimentof the present invention is a nickel manganese cobalt compositehydroxide, which is a precursor of a positive electrode active material,and which is composed of secondary particles to which primary particlescontaining a nickel, a manganese, and a cobalt are aggregated, orcomposed of the primary particles and the secondary particles, wherein asodium content contained in the nickel manganese cobalt compositehydroxide is less than 0.0005% by mass.

In this way, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a sodiumcontent.

Here, in one embodiment of the present invention, a specific surfacearea of the nickel manganese cobalt composite hydroxide may be 10 to 20m²/g.

In this way, by configuring its specific surface area to be large, it ispossible to provide a nickel manganese cobalt composite hydroxide, whichis a precursor of a positive electrode active material capable ofobtaining a lithium ion secondary battery capable of further improving abattery characteristic.

Here, in one embodiment of the present invention, a sulfate radicalcontent contained in the nickel manganese cobalt composite hydroxide maybe 0.2% by mass or less, and also, a chloride radical content may be0.01% by mass or less.

In this way, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a contentof a sulfate radical, a chloride radical, and a sodium.

Here, in one embodiment of the present invention, a value of[(d90−d10)/average particle size], which is an index indicating a spreadof a particle size distribution of the nickel manganese cobalt compositehydroxide, may be 0.55 or less.

In this way, a proportion of large particles and fine particles whenformed as a positive electrode active material will be low, so in alithium ion secondary battery using this positive electrode activematerial as a positive electrode, it is possible to obtain excellentcycle characteristic and battery output with an excellent safety.

Here, in one embodiment of the present invention, the nickel manganesecobalt composite hydroxide may be represented by a general formula:Ni_(x)Co_(y)Mn_(z)M_(t)(OH)_(2+a) wherein x+y+z+t=1, 0.20≤x≤0.80,0.10≤y≤0.50, 0.10≤z≤0.90, 0≤t≤0.10, 0≤a≤0.5, and M is at least oneselected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W).

In this way, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a sodiumcontent of the nickel manganese cobalt composite hydroxide.

Here, in one embodiment of the present invention, a content of at leastone of a potassium, a calcium, and a magnesium contained in the nickelmanganese cobalt composite hydroxide may be less than 0.0005% by mass.

In this way, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of further improvinga battery characteristic with a high void ratio, and also, capable offurther decreasing a content of impurities.

In one embodiment of the present invention, a method for producing anickel manganese cobalt composite hydroxide, which is a precursor of apositive electrode active material, and which is composed of secondaryparticles to which primary particles containing a nickel, a manganese,and a cobalt are aggregated, or composed of the primary particles andthe secondary particles, comprising: a crystallization process forobtaining a transition metal composite hydroxide by crystallizing in areaction solution obtained by adding a raw material solution containinga nickel, a manganese, and a cobalt, a solution containing an ammoniumion supplier, and an alkaline solution; and a washing process forwashing the transition metal composite hydroxide obtained in thecrystallization process by a washing liquid, wherein the alkalinesolution in the crystallization process is a mixed solution of an alkalimetal hydroxide and a carbonate, a ratio [CO₃ ²⁻]/[OH⁻] of the carbonatewith respect to the alkali metal hydroxide in the mixed solution is0.002 to 0.050, a crystallization is performed in a non-oxidizingatmosphere in the crystallization process, and the washing liquid in thewashing process is an ammonium hydrogen carbonate solution with aconcentration of 0.05 mol/L or more.

In this way, it is possible to provide a method for producing a nickelmanganese cobalt composite hydroxide, which is a precursor of a positiveelectrode active material of a lithium ion secondary battery capable ofimproving a battery characteristic, and also, capable of surelydecreasing a sodium content.

Here, in one embodiment of the present invention, the crystallizationprocess further comprises a nucleation process and a particle growthprocess, and in the nucleation process, a nucleation may be performed byadding the alkaline solution to the reaction solution such that a pHmeasured on the basis of a liquid temperature of 25 degrees Celsius willbe 12.0 to 14.0, and in the particle growth process, the alkalinesolution may be added to the reaction solution containing nuclei formedin the nucleation process such that a pH measured on the basis of aliquid temperature of 25 degrees Celsius will be 10.5 to 12.0.

In this way, it is possible to obtain a nickel manganese cobaltcomposite hydroxide having a narrow particle size distribution.

Here, in one embodiment of the present invention, the nickel manganesecobalt composite hydroxide obtained via the washing process is a nickelmanganese cobalt composite hydroxide, which is a precursor of a positiveelectrode active material, and which is composed of secondary particlesto which primary particles containing a nickel, a manganese, and acobalt are aggregated, or composed of the primary particles and thesecondary particles, and a sodium content contained in the nickelmanganese cobalt composite hydroxide may be less than 0.0005% by mass.

In this way, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a sodiumcontent.

In one embodiment of the present invention, a lithium nickel manganesecobalt composite oxide composed of secondary particles to which primaryparticles containing a lithium, a nickel, a manganese, and a cobalt areaggregated, or composed of the primary particles and the secondaryparticles, wherein a sodium content contained in the lithium nickelmanganese cobalt composite oxide is less than 0.0005% by mass.

In this way, it is possible to provide a lithium nickel manganese cobaltcomposite oxide, which is a positive electrode active material of alithium ion secondary battery capable of improving a batterycharacteristic, and also, capable of surely decreasing a sodium content.

Here, in one embodiment of the present invention, a sulfate radicalcontent contained in the lithium nickel manganese cobalt composite oxidemay be 0.15% by mass or less, and a chloride radical content may be0.005% by mass or less, and also, a Me site occupancy factor may be93.0% or more.

In this way, it is possible to provide a lithium nickel manganese cobaltcomposite oxide, which is a positive electrode active material of alithium ion secondary battery capable of further improving a batterycharacteristic, and also, capable of surely decreasing a content of asulfate radical, a chloride radical, and a sodium.

Here, in one embodiment of the present invention, a ratio of an averageparticle size of the lithium nickel manganese cobalt composite oxidedivided by an average particle size of a nickel manganese cobaltcomposite hydroxide, which is a precursor, may be 0.95 to 1.05.

In this way, it is possible to provide a lithium nickel manganese cobaltcomposite oxide, which is a positive electrode active material of alithium ion secondary battery capable of achieving a high batterycapacity and a high filling ability, and also, capable of inhibiting anaggregation by sintering.

Here, in one embodiment of the present invention, when observing 100 ormore particles of the lithium nickel manganese cobalt composite oxideselected randomly by a scanning electron microscope, a number that anaggregation of secondary particles is observed may be 5% or less withrespect to a total number of observed secondary particles.

In this way, it is possible to provide a lithium nickel manganese cobaltcomposite oxide, which is a positive electrode active material of alithium ion secondary battery capable of achieving a high batterycapacity and a high filling ability, and also, capable of inhibiting anaggregation by sintering.

Here, in one embodiment of the present invention, a content of at leastone of a potassium, a calcium, and a magnesium contained in the lithiumnickel manganese cobalt composite oxide may be less than 0.0005% bymass.

In this way, it is possible to provide a lithium nickel manganese cobaltcomposite oxide, which is a positive electrode active material of alithium ion secondary battery capable of achieving a high batterycapacity, and also, capable of further decreasing a content ofimpurities.

Here, in other embodiment of the present invention, it may be a lithiumion secondary battery comprising a positive electrode at leastcontaining the lithium nickel manganese cobalt composite oxide.

In this way, it is possible to provide a lithium ion secondary batterycomprising a positive electrode containing a lithium nickel manganesecobalt composite oxide capable of achieving a high battery capacity anda high filing ability, and also, capable of inhibiting an aggregation bysintering and surely decreasing a sodium content.

According to the present invention, it is possible to provide a nickelmanganese cobalt composite hydroxide, which is a precursor of a positiveelectrode active material of a lithium ion secondary battery capable ofimproving a battery characteristic, and also, capable of inhibiting anaggregation by sintering and surely decreasing a sodium contentespecially, a method for producing the nickel manganese cobalt compositehydroxide, a lithium nickel manganese cobalt composite oxide, and alithium ion secondary battery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional SEM photograph of a nickel manganese cobaltcomposite hydroxide relating to one embodiment of the present invention,and which is a view illustrating that an internal structure is a solidstructure.

FIG. 2 is a flow chart illustrating an outline of a method for producinga nickel manganese cobalt composite hydroxide relating to one embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

By a keen examination for solving the above problem, the inventors havefound that impurities such as a sulfate radical, a chloride radical, anda sodium are decreased to a lower concentration more efficiently, bywashing a transition metal composite hydroxide obtained in acrystallization process by using an ammonium hydrogen carbonate solutionwhich is a washing liquid containing a hydrogen carbonate (abicarbonate) in a washing process, in addition to forming an alkalinesolution to be used in the crystallization process as a mixed solutionof an alkali metal hydroxide and a carbonate, and controlling a reactionatmosphere in the crystallization process, in a production of a nickelmanganese cobalt composite hydroxide, and completed the presentinvention. Also, as mentioned in the above, the inventors have foundthat a lithium nickel manganese cobalt composite oxide, which is apositive electrode active material of a lithium ion secondary batterycapable of achieving a high battery capacity and a high filling ability,and also, capable of inhibiting an aggregation by sintering, is obtainedby using a nickel manganese cobalt composite hydroxide, in which asodium content is surely decreased, as a precursor, and completed thepresent invention. Hereinafter, explaining about preferred embodimentsof the present invention.

In addition, following explained embodiments do not unjustly limit acontent of the present invention described in claims, and modificationsare possible within a scope that does not depart from a gist of thepresent invention. Also, not all of configurations explained in thepresent embodiments are necessary as a means for solving the problem ofthe present invention. Explaining about a nickel manganese cobaltcomposite hydroxide relating to one embodiment of the present invention,a method for producing the nickel manganese cobalt composite hydroxide,a lithium nickel manganese cobalt composite oxide, and a lithium ionsecondary battery, in a following order.

1. Nickel manganese cobalt composite hydroxide2. Lithium nickel manganese cobalt composite oxide3. Method for producing nickel manganese cobalt composite hydroxide

3-1. Crystallization process

3-1-1. Nucleation process

3-1-2. Particle growth process

3-2. Washing process

4. Lithium ion secondary battery

<1. Nickel Manganese Cobalt Composite Hydroxide>

A nickel manganese cobalt composite hydroxide relating to one embodimentof the present invention is a precursor of a positive electrode activematerial, and composed of secondary particles to which primary particlescontaining a nickel, a manganese, and a cobalt are aggregated, orcomposed of the primary particles and the secondary particles.

And, it is characterized in that a sodium content contained in thenickel manganese cobalt composite hydroxide is less than 0.0005% bymass. Hereinafter, explaining about a nickel manganese cobalt compositehydroxide relating to one embodiment of the present inventionconcretely.

[Composition of Particle]

A nickel manganese cobalt composite hydroxide is preferably adjusted tohave a composition represented by a general formula:Ni_(x)Co_(y)Mn_(z)M_(t)(OH)_(2+a) (wherein x+y+z+t=1, 0.20≤x≤0.80,0.10≤y≤0.50, 0.10≤z≤0.90, 0≤t≤0.10, 0≤a≤0.5, and M is at least oneselected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, W).

In the general formula, it is preferable that x indicating a nickelcontent is 0.20≤x≤0.80. Also, it is more preferable that x indicating anickel content is x≤0.6 when considering an electric characteristic anda heat stability.

In addition, in the general formula, it is preferable that y indicatinga cobalt content is 0.10≤y≤0.50. It is possible to reduce an expansionand shrinkage behavior of a crystal lattice by a deinsertion and aninsertion of a lithium involving a charge and a discharge or animprovement of a cycle characteristic by adding a cobalt properly, butwhen y is less than 0.10, it is not possible to achieve a sufficientreduction effect of an expansion and shrinkage behavior of a crystallattice, so it is not preferable. On the other hand, when an additionamount of a cobalt is too much and y is more than 0.50, a decrease of aninitial discharge capacity will be too large, and there is a problemthat it will be disadvantageous in a cost, so it is not preferable.

In addition, it is preferable that z indicating a manganese content is0.10≤z≤0.90. When a manganese is added in this range, it is possible toimprove a safety and a durability of a battery if it is used as apositive electrode active material of the battery. When z is less than0.10, it is not possible to achieve a sufficient effect of improving asafety and a durability of the battery, on the other hand, when z ismore than 0.90, metal elements contributing to a Redox reaction will bereduced and a battery capacity will be deceased, so it is notpreferable.

An additive element M is one or more element selected from Mg, Ca, Al,Ti, V, Cr, Zr, Nb, Mo, W, and it is added to improve a batterycharacteristic such as a cycle characteristic or an outputcharacteristic. It is preferable that t indicating a content of theadditive element M is 0≤t≤0.10. When t is more than 0.10, metal elementscontributing to a Redox reaction will be reduced and a battery capacitywill be deceased, so it is not preferable.

In addition, a method for analyzing a composition of particles is notlimited particularly, but it can be determined by a chemical analysismethod, for example by an acid decomposition—inductively-coupled plasma(ICP) emission spectrometry.

[Particle Structure]

The nickel manganese cobalt composite hydroxide is composed of sphericalsecondary particles to which a plurality of primary particles areaggregated. The primary particles composing the secondary particles mayhave various shapes such as a plate shape, a needle shape, a rectangularparallelepiped shape, an elliptical shape, and a rhombohedral shape.Further, the primary particles may be aggregated in random directions.Alternatively, the primary particles aggregated radially from a centeralong a major axis direction thereof may also be applicable in thepresent invention.

The secondary particles are preferably formed by an aggregation of aplurality of plate shaped and/or needle shaped primary particles inrandom directions. The reason for this is that when the secondaryparticles have such a structure, voids are created substantiallyuniformly among the primary particles, and therefore when the nickelmanganese cobalt composite hydroxide is mixed with a lithium compoundand a mixture is fired, the fused lithium compound is distributed in thesecondary particles so that a lithium is diffused sufficiently.

It is to be noted that a method for observing shapes of the primaryparticles and the secondary particles is not limited particularly, butthe primary particles and the secondary particles may be measured byobserving a cross-section of the nickel manganese cobalt compositehydroxide with a scanning electron microscope (SEM).

[Internal Structure of Particles]

A nickel manganese cobalt composite hydroxide relating to one embodimentof the present invention is having a solid structure, and does not havea porous structure or a hollow structure at inside of secondaryparticles. It is most excellent in a particle strength as there is nospace at inside of secondary particles. Thus, a positive electrodeactive material will have a long life span.

In addition, this solid structure can be confirmed by observing a crosssection of the nickel manganese cobalt composite hydroxide particles, bya scanning electron microscope (SEM). In addition, in the nickelmanganese cobalt composite hydroxide relating to one embodiment of thepresent invention, the secondary particles are having a solid structure.For example, by further adjusting a crystallization condition, it can bea solid structure, a hollow structure, a porous structure, a combinationthereof, or they can be mixed in a certain proportion, according toneeds of a consumer regarding a production, a specification, and acharacteristic. There is an advantage that an overall composition and aparticle size can be stabilized, compared to which a solid structure, ahollow structure, and a porous structure are merely mixed.

[Average Particle Size (MV)]

The nickel manganese cobalt composite hydroxide is preferably adjustedto have an average particle size of 3 to 20 μm. If the average particlesize is less than 3 μm, a filling density of particles in a positiveelectrode formed using a resulting positive electrode active material isdecreased so that a battery capacity per volume of the positiveelectrode is undesirably decreased. On the other hand, if the averageparticle size is more than 20 μm, a specific surface area of a resultingpositive electrode active material is decreased, so that an interfacebetween the positive electrode active material and an electrolytesolution of a battery is reduced, which undesirably increases aresistance of a positive electrode and decreases an outputcharacteristic of the battery. Therefore, when the average particle sizeof the nickel manganese cobalt composite hydroxide is adjusted to bewithin a range of 3 to 20 μm, preferably 3 to 15 μm, more preferably 4to 12 μm, a lithium ion secondary battery using this positive electrodeactive material as a positive electrode material can have a high batterycapacity per volume, a high level of safety, and an excellent cyclecharacteristic.

A method for measuring an average particle size is not limitedparticularly. For example, an average particle size may be determined bya volume-based distribution measured by using a laser diffractionscattering method.

[Impurity Content]

Generally, a nickel manganese cobalt composite hydroxide contains apotassium, a calcium, a magnesium and the like, in addition to a sulfateradical, a chloride radical, and a sodium, as impurities. As theseimpurities will be a cause for deteriorating a reaction with a lithium,and also, as these impurities almost do not contribute to charge anddischarge reactions, it is preferable to reduce a content of theseimpurities by removing these impurities as much as possible.Conventionally, technologies for removing these impurities have beendisclosed, but these conventional technologies are still insufficient.

Here, a nickel manganese cobalt composite hydroxide relating to oneembodiment of the present invention is characterized in that a sodiumcontent contained in the nickel manganese cobalt composite hydroxide isless than 0.0005% by mass. In this way, it is possible to provide anickel manganese cobalt composite hydroxide, which is a precursor of apositive electrode active material of a lithium ion secondary batterycapable of improving a battery characteristic, and also, capable ofsurely decreasing a sodium content.

As mentioned in the above, in a prior art, a sodium remains for 0.001%to 0.015% by mass, and a reduction of a sodium is insufficient. Inaddition, in a prior art, there is a document describing that a sodiumcontent is a certain numerical value or less, but a composite hydroxideor a composite oxide in which a sodium content will be an extremely lowconcentration of less than 0.0005% by mass, as the nickel manganesecobalt composite hydroxide relating to one embodiment of the presentinvention or the lithium nickel manganese cobalt composite oxidedescribed in below, is not disclosed practically. According to aproduction method described in below, a sodium content with an extremelylow concentration of less than 0.0005% by mass is achieved. In this way,an aggregation by sintering when forming the lithium nickel manganesecobalt composite oxide is inhibited.

In addition, a sulfate radical content contained in the nickel manganesecobalt composite hydroxide is preferably 0.2% by mass or less, and also,a chloride radical content is preferably 0.01% by mass or less. In thisway, it is possible to provide a nickel manganese cobalt compositehydroxide, which is a precursor of a positive electrode active materialof a lithium ion secondary battery capable of improving a batterycharacteristic, and also, capable of surely decreasing a content of asulfate radical, a chloride radical, and a sodium.

A content of at least one of a potassium, a calcium, and a magnesiumcontained in the nickel manganese cobalt composite hydroxide ispreferably less than 0.0005% by mass. In this way, it is possible toprovide a nickel manganese cobalt composite hydroxide, which is aprecursor of a positive electrode active material of a lithium ionsecondary battery capable of further improving a battery characteristicwith a high void ratio, and also, capable of further decreasing acontent of impurities.

About a content of each impurity, it is possible to determine by usingan analysis method indicated in below. A potassium, a calcium, amagnesium and the like, including a sodium can be determined by an aciddecomposition—atomic absorption spectrometry, an acid decomposition—ICPemission spectrometry, or the like. In addition, a sulfate radical canbe determined by analyzing an entire sulfur content of the nickelmanganese cobalt composite hydroxide by a combustion infrared absorptionmethod, an acid decomposition—ICP emission spectrometry, or the like,and by converting this entire sulfur content into a sulfate radical (SO₄²⁻). In addition, a chloride radical can be determined by analyzing thenickel manganese cobalt composite hydroxide directly, or by analyzing achloride radical by separating a chloride radical contained in adistillation operation in a form of a silver chloride or the like, by anX-ray fluorescence (XRF) analysis.

[Particle Size Distribution]

The nickel manganese cobalt composite hydroxide is preferably adjustedsuch that a value of [(d90−d10)/average particle size], which is anindex indicating a spread of a particle size distribution of particles,is 0.55 or less.

For instance, when the nickel manganese cobalt composite hydroxide has awide particle size distribution and therefore a value of[(d90−d10)/average particle size], which is an index indicating a spreadof a particle size distribution, is more than 0.55, the nickel manganesecobalt composite hydroxide tends to contain many fine particles whoseparticle sizes are much smaller than an average particle size or manyparticles (large-sized particles) whose particle sizes are much largerthan an average particle size.

Such features of a particle size distribution at a stage of a precursorhave a great effect on a positive electrode active material obtainedafter a firing process. When a positive electrode is formed using apositive electrode active material containing many fine particles, notonly there is a possibility that a safety will be decreased as there isa risk of a heat generation by a local reaction of the fine particles,but also there is a possibility that a cycle characteristic will bedeteriorated due to a selective degradation of the fine particles havinga large specific surface area, so it is not preferable. On the otherhand, when a positive electrode is formed using a positive electrodeactive material containing many large-sized particles, there is apossibility that a battery output will be decreased due to an increasein a reaction resistance, as an adequate reaction area between anelectrolyte solution and the positive electrode active material is notprovided, so it is not preferable.

Therefore, in a particle size distribution of the nickel manganesecobalt composite hydroxide, which is a precursor, it is preferable that[(d90−d10)/average particle size] is 0.55 or less, and as a ratio offine particles or large-sized particles will be low, a lithium ionsecondary battery having a positive electrode using this positiveelectrode active material can have a high level of safety, an excellentcycle characteristic, and a high battery output.

In addition, in [(d90−d10)/average particle size] which is an indexindicating a spread of a particle size distribution, d10 means aparticle size at which a cumulative volume of particles reaches 10% of atotal volume of all particles when a number of particles in eachparticle size is counted from a smaller particle size. On the otherhand, d90 means a particle size at which a cumulative volume ofparticles reaches 90% of a total volume of all particles when a numberof particles in each particle size is counted from a smaller particlesize. A method for determining an average particle size, d90, and d10 isnot limited particularly. For example, an average particle size, d90,and d10 may be determined by a volume-based distribution measured byusing a laser diffraction scattering method.

[Specific Surface Area]

The nickel manganese cobalt composite hydroxide is preferably adjustedto have a specific surface area of 10 to 80 m²/g, and if it is a solidtype with no void in particles, it is preferably adjusted to have aspecific surface area of 10 to 20 m²/g. This is because when the nickelmanganese cobalt composite hydroxide having a specific surface area inthe above range is mixed with a lithium compound and a mixture is fired,the particles of the nickel manganese cobalt composite hydroxide cansecure a sufficient surface area to come into contact with the fusedlithium compound, and also, a particle strength of the formed positiveelectrode active material will be satisfactory.

On the other hand, if a specific surface area is less than 10 m²/g,there is a concern that when the nickel manganese cobalt compositehydroxide is mixed with a lithium compound and a mixture is fired, thenickel manganese cobalt composite hydroxide cannot sufficiently comeinto contact with the fused lithium compound so that a crystallinity ofa resulting lithium nickel manganese cobalt composite oxide will bedecreased, and a capacity of a lithium ion secondary battery using thelithium nickel manganese cobalt composite oxide as a positive electrodematerial will be decreased due to an inhibition of Li diffusion in asolid phase. In addition, if a specific surface area is more than 80m²/g, there is a possibility that when the nickel manganese cobaltcomposite hydroxide is mixed with a lithium compound and a mixture isfired, a crystal growth proceeds excessively and a cation mixing occurs,in which nickels enter into lithium layers of a resulting lithiumtransition metal composite oxide which is a layered compound, and acharge and discharge capacity will be decreased, so it is notpreferable.

A method for measuring a specific surface area is not limitedparticularly. For example, a specific surface area may be determined bya nitrogen gas adsorption and desorption method by a BET multipointmethod or a BET one-point method.

In FIG. 1, a sectional SEM photograph of a nickel manganese cobaltcomposite hydroxide relating to one embodiment of the present inventionis illustrated. As such, in the nickel manganese cobalt compositehydroxide relating to one embodiment of the present invention, aninternal structure is a solid structure as illustrated in FIG. 1.

According to the nickel manganese cobalt composite hydroxide relating toone embodiment of the present invention, it is possible to provide aprecursor of a positive electrode active material of a lithium ionsecondary battery capable of improving a battery characteristic, andalso, capable of surely decreasing a sodium content especially. Inaddition, as mentioned in the above, by using the nickel manganesecobalt composite hydroxide in which a sodium content is surely decreasedas a precursor, it is possible to provide a lithium nickel manganesecobalt composite oxide, which is a positive electrode active material ofa lithium ion secondary battery capable of achieving a high batterycapacity and a high filling ability, and also, capable of inhibiting anaggregation by sintering.

<2. Lithium Nickel Manganese Cobalt Composite Oxide>

A lithium nickel manganese cobalt composite oxide relating to oneembodiment of the present invention is composed of secondary particlesto which primary particles containing a lithium, a nickel, a manganese,and a cobalt are aggregated, or composed of the primary particles andthe secondary particles. And, it is characterized in that a sodiumcontent contained in the lithium nickel manganese cobalt composite oxideis less than 0.0005% by mass.

In addition, a sulfate radical content contained in the lithium nickelmanganese cobalt composite oxide is preferably 0.15% by mass or less, achloride radical content is preferably 0.005% by mass or less, and also,a Me site occupancy factor is preferably 93.0% or more.

A ratio of an average particle size of the lithium nickel manganesecobalt composite oxide divided by an average particle size of a nickelmanganese cobalt composite hydroxide, which is a precursor, i.e. “MV oflithium nickel manganese cobalt composite oxide/MV of nickel manganesecobalt composite hydroxide” (hereinafter, also referred to as “MVratio”) can be evaluated as an index indicating an aggregation bysintering. A range of this MV ratio is preferably 0.95 to 1.05, and morepreferably 0.97 to 1.03.

When this MV ratio is in the above range, a positive electrode activematerial is composed of a lithium nickel manganese cobalt compositeoxide, in which an aggregation of the secondary particles themselves inassociation with an aggregation by sintering hardly occurs. A secondarybattery using such positive electrode active material is having a highfilling ability and a high battery capacity, and is excellent in auniformity with less variation in a characteristic.

On the other hand, when the MV ratio is more than 1.05, a specificsurface area and a filling ability may be decreased in association withan aggregation by sintering. In a secondary battery using such positiveelectrode active material, an output characteristic and a batterycapacity may be decreased, as a reactivity will be deteriorated. Inaddition, when charged and discharged repeatedly, there is a risk ofimpairing a cycle characteristic significantly, as a collapse occursselectively from a portion with a weak strength where secondaryparticles themselves are aggregated in a positive electrode, so whenestimated safely, the MV ratio is preferably 1.05 or less, and morepreferably 1.03 or less.

Further, when the MV ratio is less than 0.95, it is considered that aparticle size is decreased as some primary particles are lost fromsecondary particles in a production process of a lithium nickelmanganese cobalt composite oxide, and thereby, a particle sizedistribution may be wide, so the MV ratio is preferably 0.95 or more,and more preferably 0.97 or more.

In addition, a MV of a nickel manganese cobalt composite hydroxide meansa MV of a nickel manganese cobalt composite hydroxide used as aprecursor when producing a lithium nickel manganese cobalt compositeoxide. Also, if a crushing process is performed, a MV of a lithiumnickel manganese cobalt composite oxide means a MV of a lithium nickelmanganese cobalt composite oxide after the crushing process. Inaddition, a MV of each particle may be measured by a laser diffractionscattering particle size distribution measuring device, and a MV of eachparticle means a particle size in which an accumulated volume will be anaverage value of a total volume of all particles when accumulating anumber of particles in each particle size from a smaller particle size.

In addition, when observing 100 or more particles of a lithium nickelmanganese cobalt composite oxide selected randomly by a scanningelectron microscope (SEM), a number that an aggregation of secondaryparticles is observed may be 5% or less, 3% or less, or 2% or less withrespect to a total number of observed secondary particles. When a numberin which an aggregation of secondary particles is observed is in theabove range, it indicates that an aggregation by sintering of secondaryparticles is inhibited sufficiently. Also, when a MV of a positiveelectrode active material is in the above range, a number in which anaggregation of secondary particles is observed can be easily controlledto be in the above range. In addition, a magnification of a scanningelectron microscope (SEM) when observing is, for example about 1000times.

When a number in which an aggregation of secondary particles is observedis 5% or less with respect to a total number of observed secondaryparticles, a positive electrode active material is composed of a lithiumnickel manganese cobalt composite oxide, in which an aggregation of thesecondary particles themselves in association with an aggregation bysintering hardly occurs. A secondary battery using such positiveelectrode active material is having a high filling ability and a highbattery capacity, and is excellent in a uniformity with less variationin a characteristic.

On the other hand, when a number in which an aggregation of secondaryparticles is observed is more than 5% with respect to a total number ofobserved secondary particles, a specific surface area and a fillingability may be decreased in association with an aggregation bysintering. In a secondary battery using such positive electrode activematerial, an output characteristic and a battery capacity may bedecreased, as a reactivity will be deteriorated. In addition, whencharged and discharged repeatedly, there is a risk of impairing a cyclecharacteristic significantly, as a collapse occurs selectively from aportion with a weak strength where secondary particles themselves areaggregated in a positive electrode, so when estimated safely, it ispreferably 5% or less.

A content of at least one of a potassium, a calcium, and a magnesiumcontained in the lithium nickel manganese cobalt composite oxide ispreferably less than 0.0005% by mass. In this way, it is possible toprovide a lithium nickel manganese cobalt composite oxide, which is apositive electrode active material of a lithium ion secondary batterycapable of achieving a high battery capacity, and also, capable offurther decreasing a content of impurities.

The nickel manganese cobalt composite hydroxide can produce a lithiumnickel manganese cobalt composite oxide by mixing with a lithiumcompound and firing a mixture. And, the lithium nickel manganese cobaltcomposite oxide can be used as a raw material of a positive electrodeactive material of a lithium ion secondary battery.

The lithium nickel manganese cobalt composite oxide used as a positiveelectrode active material can be obtained via a firing process aftermixing a nickel manganese cobalt composite hydroxide, which is aprecursor, with a lithium compound such as a lithium nitrate (LiNO₃:Melting point 261 degrees Celsius), a lithium chloride (LiCi: Meltingpoint 613 degrees Celsius), and a lithium sulfate (Li₂SO₄: Melting point859 degrees Celsius), including a lithium carbonate (Li₂CO₃: Meltingpoint 723 degrees Celsius) and a lithium hydroxide (LiOH: Melting point462 degrees Celsius).

Regarding a lithium compound, it is especially preferable to use alithium carbonate or a lithium hydroxide considering an easiness ofhandling and a stability of quality.

In this firing process, a carbonate radical, a hydroxyl group, a nitrateradical, a chloride radical, and a sulfate radical, which may becomponents of a lithium compound, will be volatilized, but a smallproportion of them remains in a positive electrode active material.About a solid structure of secondary particles, in addition to aparticle size distribution and a specific surface area, includingnonvolatile components such as a sodium, characteristics of a nickelmanganese cobalt composite hydroxide, which is a precursor, will bealmost succeeded.

According to a lithium nickel manganese cobalt composite oxide relatingto one embodiment of the present invention, it is possible to provide apositive electrode active material of a lithium ion secondary batterycapable of improving a battery characteristic, and also, capable ofsurely decreasing a sodium content especially.

<3. Method for Producing Nickel Manganese Cobalt Composite Hydroxide>

Next, explaining about a method for producing a nickel manganese cobaltcomposite hydroxide relating to one embodiment of the present invention,using FIG. 2. A method for producing a nickel manganese cobalt compositehydroxide relating to one embodiment of the present invention is amethod for producing a precursor of a positive electrode active materialcomposed of secondary particles to which primary particles containing anickel, a manganese, and a cobalt are aggregated, or composed of theprimary particles and the secondary particles. And, as illustrated inFIG. 2, it comprises a crystallization process S10 and a washing processS20.

In a crystallization process S10, a transition metal composite hydroxideis obtained by crystallizing in a reaction solution obtained by adding araw material solution containing a nickel, a manganese, and a cobalt, asolution containing an ammonium ion supplier, and an alkaline solution.And, in a washing process S20, the transition metal composite hydroxideobtained in the crystallization process S10 is washed by a washingliquid.

In addition, the alkaline solution in the crystallization process S10 isa mixed solution of an alkali metal hydroxide and a carbonate, a molarratio [CO₃ ²⁻]/[OH⁻] of the carbonate with respect to the alkali metalhydroxide of the mixed solution is 0.02 to 0.05, and in thecrystallization process S10, a crystallization is performed in anon-oxidizing atmosphere, and the washing liquid in the washing processS20 is an ammonium hydrogen carbonate solution with a concentration of0.05 mol/L or more. Hereinafter, explaining in detail per process.

<3-1. Crystallization Process>

In a crystallization process S10, a transition metal composite hydroxideis obtained by crystallizing in a reaction solution obtained by adding araw material solution containing a nickel, a manganese, and a cobalt, asolution containing an ammonium ion supplier, and an alkaline solution.

In addition, the crystallization process S10 is further having anucleation process S11 and a particle growth process S12 preferably. Inthe nucleation process S11, a nucleation is performed in a reactionsolution by adding an alkaline solution such that a pH of the reactionsolution measured on the basis of a liquid temperature of 25 degreesCelsius will be 12.0 to 14.0, and in the particle growth process S12, analkaline solution is preferably added to a reaction solution containingnuclei formed in the nucleation process S11 such that a pH of thereaction solution measured on the basis of a liquid temperature of 25degrees Celsius will be 10.5 to 12.0. Detail will be described later.

In a conventional continuous crystallization process, a nucleationreaction and a particle growth reaction proceed simultaneously in thesame reaction tank, so a particle size distribution of an obtainedprecursor was widespread. On the other hand, in a method for producing anickel manganese cobalt composite hydroxide of the present invention, atime when a nucleation reaction mainly occurs (nucleation process) and atime when a particle growth reaction mainly occurs (particle growthprocess) are clearly separated from each other. Therefore, even whenboth processes are performed in the same reaction tank, a transitionmetal composite hydroxide having a narrow particle size distribution isobtained. Also, it is possible to reduce impurities such as a sulfateradical by using a mixed solution of an alkali metal hydroxide and acarbonate as an alkaline solution.

Hereinafter, explaining in detail about a condition and a material to beused in a method for producing a nickel manganese cobalt compositehydroxide of the present invention.

[Raw Material Solution Containing Nickel, Manganese, and Cobalt]

Metal salts used in a raw material solution containing a nickel, amanganese, and a cobalt, such as a nickel salt, a manganese salt, and acobalt salt, are not limited particularly as long as it is awater-soluble compound, but a sulfate, a nitrate, a chloride and elsemay be used. For example, a nickel sulfate, a manganese sulfate, and acobalt sulfate are preferably used.

Also, it is possible to form a raw material solution by mixing acompound containing one or more additive elements M at a predeterminedratio according to need. In the crystallization process S10 of thiscase, it is preferable to use a compound containing one or more additiveelements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, W, and forexample, a titanium sulfate, an ammonium peroxotitanate, a titaniumpotassium oxalate, a vanadium sulfate, an ammonium vanadate, a chromiumsulfate, a potassium chromate, a zirconium sulfate, a zirconium nitrate,a niobium oxalate, an ammonium molybdate, a sodium tungstate, anammonium tungstate and else may be used.

Also, a nickel manganese cobalt composite hydroxide may be coated with acompound containing one or more additive elements M, by adjusting a pHof a slurry obtained by mixing the nickel manganese cobalt compositehydroxide obtained by a crystallization with an aqueous solutioncontaining one or more additive elements M.

A concentration of the raw material solution is preferably 1 mol/L to2.6 mol/L, more preferably 1 mol/L to 2.2 mol/L as a concentration oftotal metal salts. If a concentration of the raw material solution isless than 1 mol/L, a concentration of a resulting hydroxide slurry willbe low, and which deteriorates productivity. On the other hand, if aconcentration of the raw material solution is more than 2.6 mol/L, thereis a risk that a crystal deposition or a freezing occurs at −5 degreesCelsius or less, and that pipes of an equipment will be clogged, so thepipes need to be kept warm or heated, which increases a cost.

Further, an amount of the raw material solution supplied to a reactiontank is preferably adjusted such that a concentration of a crystallizedproduct, when a crystallization reaction is finished, is generally 30g/L to 250 g/L, and preferably 80 g/L to 150 g/L. If a concentration ofthe crystallized product is less than 30 g/L, an aggregation of primaryparticles may be insufficient. If a concentration of the crystallizedproduct is more than 250 g/L, a diffusion of an added mixed aqueoussolution in the reaction tank may be insufficient, so that particles maynot grow uniformly.

[Ammonium Ion Supplier]

An ammonium ion supplier in a reaction solution is not limitedparticularly as long as it is a water-soluble compound, and an ammoniawater, an ammonium sulfate, an ammonium chloride, an ammonium carbonate,an ammonium fluoride and else may be used. For example, an ammonia wateror an ammonium sulfate is preferably used.

A concentration of ammonium ions in the reaction solution is adjusted tobe preferably 3 g/L to 25 g/L, more preferably 5 g/L to 20 g/L, evenmore preferably 5 g/L to 15 g/L. When ammonium ions are present in thereaction solution, metal ions, especially Ni ions form an amminecomplex, so that a solubility of metal ions will be increased. Thispromotes a growth of primary particles, so that dense particles of thenickel manganese cobalt composite hydroxide are likely to be obtained.Further, since a solubility of metal ions is stabilized, particles ofthe nickel manganese cobalt composite hydroxide uniform in a shape and aparticle size are likely to be obtained. Particularly, by making aconcentration of ammonium ions in the reaction solution to be 3 g/L to25 g/L, more dense particles of the composite hydroxide uniform in ashape and a particle size are likely to be obtained.

If a concentration of ammonium ions in the reaction solution is lessthan 3 g/L, a solubility of metal ions may be unstable, so that primaryparticles uniform in a shape and a particle size are not formed, andparticles having a wide particle size distribution may be obtained asgel nuclei are generated. On the other hand, if a concentration ofammonium ions in the reaction solution is more than 25 g/L, a solubilityof metal ions may be increased excessively, and an amount of metal ionsremaining in the reaction solution may be increased, so that acomposition deviation may occur. A concentration of ammonium ions can bemeasured by an ion electrode method (ion meter).

[Alkaline Solution]

An alkaline solution is prepared as a mixed solution of an alkali metalhydroxide and a carbonate. In the alkaline solution, a molar ratio ofthe carbonate to the alkali metal hydroxide, which is represented by[CO₃ ²⁻]/[OH⁻ ], is 0.002 to 0.050, preferably 0.005 to 0.030, morepreferably 0.010 to 0.025.

When the alkaline solution is a mixed solution of an alkali metalhydroxide and a carbonate, anions such as sulfate radicals and chlorideradicals that remain as impurities in the nickel manganese cobaltcomposite hydroxide obtained in the crystallization process S10 can beremoved by substituting to carbonate radicals. The carbonate radicalsare volatilized preferentially in a process to mix the nickel manganesecobalt composite hydroxide with a lithium compound and to fire amixture, as carbonate radicals are more likely to be volatilized by anignition compared to the sulfate radicals, the chloride radicals, andthe like, so the carbonate radicals will not be remained in a lithiumnickel manganese cobalt composite oxide which is a positive electrodematerial.

If the molar ratio [CO₃ ²⁻]/[OH] of the carbonate to the alkali metalhydroxide is less than 0.002, a substitution of impurities such assulfate radicals and chloride radicals derived from raw materials tocarbonate ions will be insufficient in the crystallization process S10,so these impurities are likely to be incorporated into the nickelmanganese cobalt composite hydroxide. On the other hand, even when [CO₃²⁻]/[OH⁻] is more than 0.050, an effect to reduce sulfate radicals andchloride radicals, which are impurities derived from raw materials, isnot enhanced, so excessively added carbonates will increase a cost.

The alkali metal hydroxide is preferably at least one selected from alithium hydroxide, a sodium hydroxide, and a potassium hydroxide, as anaddition amount of such water-soluble compound can be controlled easily.

The carbonate is preferably at least one selected from a sodiumcarbonate, a potassium carbonate, and an ammonium carbonate, as anaddition amount of such water-soluble compound can be controlled easily.

In addition, a method for adding the alkaline solution to the reactiontank is not limited particularly, and the alkaline solution may be addedby a pump that can control a flow rate, such as a metering pump, suchthat a pH of the reaction solution will be maintained in a rangedescribed in below.

[pH Control]

It is more preferable that the crystallization process S10 comprises: anucleation process S11 in which a nucleation is performed by adding analkaline solution to a reaction solution such that a pH of the reactionsolution measured on the basis of a liquid temperature of 25 degreesCelsius will be 12.0 to 14.0; and a particle growth process S12 in whichnuclei formed in the nucleation process S11 are grown by controlling asolution for particle growth containing the nuclei by adding an alkalinesolution such that a pH of the solution for particle growth measured onthe basis of a liquid temperature of 25 degrees Celsius will be 10.5 to12.0.

That is, a nucleation reaction and a particle growth reaction do notproceed at the same time in the same vessel, but a time when anucleation reaction mainly occurs (nucleation process S11) and a timewhen a particle growth reaction mainly occurs (particle growth processS12) are clearly separated from each other. Hereinafter, explaining indetail about the nucleation process S11 and the particle growth processS12.

<3-1-1. Nucleation Process>

In the nucleation process S11, a pH of the reaction solution iscontrolled to be in a range of 12.0 to 14.0 as a pH measured on thebasis of a liquid temperature of 25 degrees Celsius. If a pH is morethan 14.0, there is a problem that excessively fine nuclei are formed,so that the reaction aqueous solution will be gelled. On the other hand,if a pH is less than 12.0, a nucleus growth reaction occurs togetherwith a nucleation, so that non-uniform nuclei will be formed as a rangeof a particle size distribution of formed nuclei will be wide.

Therefore, when a pH of the reaction solution is controlled to be 12.0to 14.0 in the nucleation process S11, a growth of nuclei is inhibitedand almost only nucleation can occur, so that uniform nuclei are formedand a range of a particle size distribution will be narrower.

<3-1-2. Particle Growth Process>

In the particle growth process S12, a pH of the reaction solution needsto be controlled to be in a range of 10.5 to 12.0, preferably 11.0 to12.0 as a pH measured on the basis of a liquid temperature of 25 degreesCelsius. If a pH is more than 12.0, many nuclei are newly formed so thatfine secondary particles are formed, which makes it impossible to obtaina nickel manganese cobalt composite hydroxide having an excellentparticle size distribution. Further, if a pH is less than 10.5, asolubility of metal ions by ammonium ions is increased, so that metalions remaining in the solution without being deposited will beincreased, and a production efficiency may be deteriorated.

That is, when a pH of the reaction solution is controlled to be 10.5 to12.0 in the particle growth process S12, only a growth of nuclei formedin the nucleation process S11 occurs preferentially, and a formation ofnew nuclei can be inhibited, so that it is possible to obtain a uniformnickel manganese cobalt composite hydroxide having a narrower particlesize distribution.

It is to be noted that when a pH is 12.0, the reaction solution is undera boundary condition between a nucleation and a particle growth. In thiscase, either the nucleation process or the particle growth process maybe performed depending on a presence of nuclei in the reaction solution.That is, when a pH in the particle growth process S12 is adjusted to12.0, after adjusting a pH in the nucleation process S11 to be higherthan 12.0 to form a large amount of nuclei, a growth of nuclei occurspreferentially as a large amount of nuclei are present in the reactionsolution, and the nickel manganese cobalt composite hydroxide having anarrower particle size distribution and a relatively large particle sizeis obtained.

On the other hand, when nuclei are not present in the reaction solution,that is, when a pH is adjusted to 12.0 in the nucleation process S11, anucleation occurs preferentially as there is no nucleus to grow, andformed nuclei can grow by adjusting a pH in the particle growth processS12 to be less than 12.0, so that an excellent nickel manganese cobaltcomposite hydroxide can be obtained.

In either case, a pH in the particle growth process S12 shall becontrolled to be lower than a pH in the nucleation process S11. In orderto clearly separate a nucleation and a particle growth from each other,a pH in the particle growth process S12 is preferably lower than a pH inthe nucleation process S11 by 0.5 or more, more preferably by 1.0 ormore.

As described above, by clearly separating the nucleation process S11 andthe particle growth process S12 from each other by controlling a pH, anucleation occurs preferentially and a growth of nuclei hardly occurs inthe nucleation process S11, and on the other hand, only a growth ofnuclei occurs and new nuclei are hardly formed in the particle growthprocess S12. Therefore, uniform nuclei having a narrow particle sizedistribution can be formed in the nucleation process S11, and the nucleican be grown uniformly in the particle growth process S12. Therefore, inthe method for producing the nickel manganese cobalt compositehydroxide, it is possible to obtain uniform nickel manganese cobaltcomposite hydroxide particles having a narrower particle sizedistribution.

[Temperature of Reaction Solution]

A temperature of the reaction solution in the reaction tank ispreferably set to 20 to 80 degrees Celsius, more preferably 30 to 70degrees Celsius, even more preferably 35 to 60 degrees Celsius. If atemperature of the reaction solution is less than 20 degrees Celsius, anucleation is likely to occur due to a low solubility of metal ions,which makes it difficult to control a nucleation. On the other hand, ifa temperature of the reaction solution is more than 80 degrees Celsius,a volatilization of ammonia is promoted, so the ammonium ion supplierneeds to be added excessively to maintain a predetermined ammoniaconcentration, which increases a cost.

[Reaction Atmosphere]

A particle size and a particle structure of the nickel manganese cobaltcomposite hydroxide are also controlled by a reaction atmosphere in thecrystallization process S10. Therefore, in the crystallization processS10, a crystallization is performed in a non-oxidizing atmosphere. Whenan atmosphere in the reaction tank during the crystallization processS10 is controlled to be a non-oxidizing atmosphere, a growth of primaryparticles that constitute a nickel manganese cobalt composite hydroxideis promoted, so that secondary particles with an appropriately largeparticle size are formed from large and dense primary particles. Thus,it will be a solid type nickel manganese cobalt composite hydroxide asillustrated in FIG. 1. On the other hand, when an atmosphere in thereaction tank during the crystallization process S10 is controlled to bean oxidizing atmosphere, a growth of primary particles that constitute anickel manganese cobalt composite hydroxide is inhibited, so thatsecondary particles with a space at a center of a particle, or in whichmany fine voids are dispersed, are formed from fine primary particles.

By the way, a non-oxidizing atmosphere is indicating a mixed atmosphereof an inert gas and an oxygen with an oxygen concentration of 5.0% byvolume or less, preferably 2.5% by volume or less, more preferably 1.0%by volume or less. As a means for maintaining a space in the reactiontank to be such a non-oxidizing atmosphere, to circulate an inert gassuch as a nitrogen into a space in the reaction tank, and further, tobubble an inert gas in the reaction solution, can be cited. In addition,in the crystallization process S10, a preferable flow rate of a bubblingis 3 to 7/min, and more preferably about 5 L/min.

On the other hand, an oxidizing atmosphere is indicating an atmospherewith an oxygen concentration of more than 5.0% by volume, preferable10.0% by volume or more, more preferably 15.0% by volume or more. As ameans for maintaining a space in the reaction tank to be such anoxidizing atmosphere, to circulate an air or the like into a space inthe reaction tank, and further, to bubble an air or the like in thereaction solution, can be cited.

When forming a solid structure as the nickel manganese cobalt compositehydroxide relating to one embodiment of the present invention, anatmosphere in the reaction tank is preferably controlled to be an inertatmosphere, or a non-oxidizing atmosphere in which an oxygenconcentration is controlled to be 0.2% by volume or less, during thecrystallization process S10.

In addition, it is explained about the nucleation process S11 and theparticle growth process S12 in the above, but a control of the reactionatmosphere is performed simultaneously while proceeding a nucleation anda particle growth.

<3-2. Washing Process>

In a washing process S20, a transition metal composite hydroxideobtained in the crystallization process S10 is washed by a washingliquid.

[Type of Washing Liquid]

In the washing process S20, it is washed by a washing liquid based on acarbonate, a hydrogen carbonate (a bicarbonate), and a hydroxide of analkali metal salt or an ammonium salt. Preferably, the transition metalcomposite hydroxide is washed by using a washing liquid in which acarbonate, a hydrogen carbonate (a bicarbonate), or a mixture thereof isdissolved in a water.

In this way, anions of impurities such as a sulfate radical and achloride radical can be removed efficiently by using a substitutionreaction with carbonate ions and hydrogen carbonate ions (bicarbonateions) in the washing liquid. In addition, by using a carbonate and ahydrogen carbonate (a bicarbonate), it is possible to inhibit a mixingof an alkali metal such as a sodium, compared to a case using ahydroxide. In addition, in a transition metal composite hydroxide with avoid structure, it is difficult to remove impurities in a particle whena hydroxide is used, and also in this point, it is effective to use acarbonate and a hydrogen carbonate (a bicarbonate).

As a carbonate, it is preferable to select a potassium carbonate, and asa hydrogen carbonate (a bicarbonate), it is preferable to select apotassium hydrogen carbonate, or an ammonium hydrogen carbonate. Inaddition, among a carbonate and a hydrogen carbonate (a bicarbonate), byselecting an ammonium salt, cations of impurities such as a sodium canbe removed efficiently by using a substitution reaction with ammoniumions in the washing liquid. Further, among ammonium salt, by selectingan ammonium hydrogen carbonate (an ammonium bicarbonate), cations of asodium or the like can be removed most efficiently.

It is considered that not only a substitution reaction between cationsof a sodium or the like and ammonium ions, but also a characteristic ofan ammonium hydrogen carbonate (an ammonium bicarbonate) more excellentthan other salts, that is a high foaming efficiency of a carbonate gaswhen used as the washing liquid, is contributing significantly forremoving cations of a sodium or the like.

[Concentration and pH]

A concentration of an ammonium hydrogen carbonate solution which is awashing liquid is 0.05 mol/L or more. When the concentration is lessthan 0.05 mol/L, there is a risk that an effect for removing impuritiessuch as a sulfate radical, a chloride radical, a sodium and the likewill be decreased. In addition, when the concentration is 0.05 mol/L ormore, an effect for removing these impurities will not be changed.Therefore, when an excess amount of an ammonium hydrogen carbonate (anammonium bicarbonate) is added, a cost will be increased, and also,there will be an effect on an environmental load such as an effluentstandard, so it is preferable to set an upper limit of the concentrationto about 1.0 mol/L.

In addition, it is not necessary to adjust a pH of an ammonium hydrogencarbonate particularly when the concentration is 0.05 mol/L or more, andit is fine with a pH in a course of an event. For instance, when theconcentration is from 0.05 to 1.0 mol/L, its pH will be in a range ofabout 8.0 to 9.0.

[Liquid Temperature]

A liquid temperature of an ammonium hydrogen carbonate which is awashing liquid is not limited particularly, but it is preferably 15 to50 degrees Celsius. When the liquid temperature is within the aboverange, a substitution reaction with impurities and a foaming effect of acarbonate gas generated from an ammonium hydrogen carbonate will beexcellent, and a removal of impurities proceeds efficiently.

[Liquid Amount]

A liquid amount of an ammonium hydrogen carbonate is preferably 1 to 20L with respect to 1 kg of a nickel manganese cobalt composite hydroxide(as a slurry concentration, it is 50 to 1000 g/L). When the liquidamount is less than 1 L, an effect for removing impurities may not beobtained sufficiently. In addition, even when the liquid amount of morethan 20 L is used, an effect for removing impurities will not bechanged, but with an excessive liquid amount, a cost will be increased,and there will be an effect on an environmental load such as an effluentstandard, and also, it will be a cause of an increase in a load of adrainage volume in a waste water treatment.

[Washing Time]

A washing time by an ammonium hydrogen carbonate is not limitedparticularly, as long as impurities are removed sufficiently, butnormally, it is 0.5 to 2 hours.

[Washing Method]

As a washing method, 1) a general washing method to filter afterperforming a stirring washing a slurry formed by adding a nickelmanganese cobalt composite hydroxide to an ammonium hydrogen carbonatesolution, or 2) a liquid passing washing for passing through an ammoniumhydrogen carbonate solution by supplying a slurry containing a nickelmanganese cobalt composite hydroxide generated by a neutralizationcrystallization to a filter such as a filter press, can be performed.The liquid passing washing is more preferable as it is having a higheffect for removing impurities and a high productivity, and as it iscapable of performing a filtering and a washing in a same equipmentcontinuously.

In addition, after washing by an ammonium hydrogen carbonate solution,there is a case that a washing liquid containing impurities washed outby a substitution reaction is adhering to a nickel manganese cobaltcomposite hydroxide, so it is preferable to wash with a water at last.Further, after washed with a water, it is preferable to perform a dryingprocess (unillustrated) for drying a water adhered to a filtered nickelmanganese cobalt composite hydroxide.

A nickel manganese cobalt composite hydroxide obtained via the washingprocess S20 is a nickel manganese cobalt composite hydroxide, which is aprecursor of a positive electrode active material, and which is composedof secondary particles to which primary particles containing a nickel, amanganese, and a cobalt are aggregated, or composed of the primaryparticles and the secondary particles, wherein a sodium contentcontained in the nickel manganese cobalt composite hydroxide is lessthan 0.0005% by mass.

According to a method for producing a nickel manganese cobalt compositehydroxide relating to one embodiment of the present invention, it ispossible to provide a method for producing a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a sodiumcontent especially.

<4. Lithium Ion Secondary Battery>

A lithium ion secondary battery relating to one embodiment of thepresent invention is characterized in that it is having a positiveelectrode containing the lithium nickel manganese cobalt compositeoxide. In addition, the lithium ion secondary battery may be composed bycomponents similar to a general lithium ion secondary battery, and forexample, it contains a positive electrode, a negative electrode, and anon-aqueous electrolyte. In addition, an embodiment explained in belowis only an example, and a lithium ion secondary battery of the presentembodiment can be performed in forms with various modifications andimprovements based on a knowledge of a person skilled in the art, basedon the embodiment described in the present description. In addition, anintended use of a lithium ion secondary battery of the presentembodiment is not limited particularly.

(a) Positive Electrode

A positive electrode of a lithium ion secondary battery is produced, forexample as below, by using the above-mentioned lithium nickel manganesecobalt composite oxide which is a positive electrode active material. Atfirst, a powdery positive electrode active material, a conductivematerial, and a binding agent are mixed, and according to need, anactivated carbon or a solvent intended to control a viscosity are added,and these materials are kneaded to produce a positive electrode mixturepaste. A mixing ratio of each component in the positive electrodemixture paste is similar to which of a positive electrode of a generallithium ion secondary battery, and for example, when a total mass of asolid content in the positive electrode mixture paste excluding asolvent is 100 mass parts, a content of the positive electrode activematerial is preferably 60 to 95 mass parts, a content of the conductivematerial is preferably 1 to 20 mass parts, and a content of the bindingagent is preferably 1 to 20 mass parts.

The obtained positive electrode mixture paste is applied, for example ona surface of a current collector made of an aluminum foil, and dried toscatter the solvent. In addition, it may be pressed by a roll pressdevice or the like, in order to increase an electrode density accordingto need. In this way, a sheet-like positive electrode can be produced.The sheet-like positive electrode can be used for a production of abattery by cutting or the like into an appropriate size according to anaimed battery. However, a method for producing the positive electrode isnot limited to the above exemplified method, and other method may beused.

As the conductive material, for example a graphite (natural graphite,artificial graphite, expanded graphite, or the like), or a carbon blackmaterial such as an acetylene black or a Ketjen black, may be used.

The binding agent serves a function to bind active material particles,and for example, a polyvinylidene fluoride (PVDF), apolytetrafluoroethylene (PTFE), a fluororubber, an ethylene propylenediene rubber, a styrene butadiene, a cellulose resin, a polyacrylic acidor the like, may be used as the binding agent.

In addition, according to need, a solvent for dissolving the bindingagent can be added to a positive electrode mixture to disperse thepositive electrode active material, the conductive material, and anactivated carbon. As the solvent, an organic solvent such asN-methyl-2-pyrrolidone can be used concretely. In addition, theactivated carbon can be added to the positive electrode mixture, inorder to increase an electric double layer capacity.

(b) Negative Electrode

As a negative electrode, a metal lithium, a lithium alloy, or the like,or a negative electrode mixture may be used. A negative electrodemixture paste is prepared by mixing the binding agent to a negativeelectrode active material capable of an insertion and a deinsertion oflithium ions, and by adding an appropriate solvent, and the negativeelectrode mixture paste is applied on a surface of a metal foil currentcollector such as a copper, and dried, and compressed to increase anelectrode density according to need to form the negative electrodemixture to be used.

As the negative electrode active material, for example, an organiccompound fired body such as a natural graphite, an artificial graphiteand a phenol resin, and a powder body of a carbon material such as acoke may be used. In this case, as the binding agent for the negativeelectrode, a fluorine-containing resin such as a PVDF may be used aswell as the positive electrode, and as a solvent for dispersing theseactive material and binding agent, an organic solvent such asN-methyl-2-pyrrolidone may be used.

(c) Separator

A separator is arranged to be interposed between the positive electrodeand the negative electrode. The separator retains an electrolyte byseparating the positive electrode and the negative electrode, and forexample, a thin film of a polyethylene, a polypropylene or the likehaving numerous fine holes may be used.

(d) Non-Aqueous Electrolyte

As a non-aqueous electrolyte, a non-aqueous electrolyte solution may beused. As the non-aqueous electrolyte solution, an electrolyte solutionin which a lithium salt is dissolved in an organic solvent as asupporting salt may be used. Also, as the non-aqueous electrolytesolution, an electrolyte solution in which a lithium salt is dissolvedin an ionic liquid may be used. In addition, the ionic liquid iscomposed of cations and anions other than a lithium ion, and which is asalt in a form of a liquid in a normal temperature.

As the organic solvent, it is possible to use one kind solely or bymixing two kinds or more selected from: a cyclic carbonate such as anethylene carbonate, a propylene carbonate, a butylene carbonate, and atrifluoro propylene carbonate; a chain carbonate such as a diethylcarbonate, a dimethyl carbonate, an ethyl methyl carbonate, and adipropyl carbonate; an ether compound such as a tetrahydrofuran, a2-methyl tetrahydrofuran, and a dimethoxyethane; a sulfur compound suchas an ethyl methyl sulfone and a butane sultone; and a phosphor compoundsuch as a triethyl phosphate and a trioctyl phosphate.

As the supporting salt, LiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂ and acombined salt thereof may be used. Further, the non-aqueous electrolytesolution may contain a radical scavenger, a surfactant, a flameretardant or the like.

In addition, as the non-aqueous electrolyte, a solid electrolyte may beused. The solid electrolyte is having a characteristic to resist a highvoltage. As the solid electrolyte, inorganic solid electrolyte andorganic solid electrolyte may be cited.

As the inorganic solid electrolyte, an oxide-based solid electrolyte, asulfide-based solid electrolyte or the like may be used.

As the oxide-based solid electrolyte, it is not limited particularly,and any solid electrolyte may be used as long as it contains an oxygen(O), and also, it is having a lithium ion conductivity and an electroninsulating property. As the oxide-based solid electrolyte, for example,a lithium phosphate (Li₃PO₄), Li₃PO₄N_(x), LiBO₂N_(x), LiNbO₃, LiTaO₃,Li₂SiO₃, Li₄SiO₄—Li₃PO₄, Li₄SiO₄—Li₃VO₄, Li₂O—B₂O₃—P₂O₅, Li₂O—SiO₂,Li₂O—B₂O₃—ZnO, Li_(1+x)Al_(x)Ti_(2-x)(PO₄)₃ (0≤x≤1),Li_(1+x)Al_(x)Ge_(2-x)(PO₄)₃ (0≤x≤1), LiTi₂(PO₄)₃,Li_(3-x)La_(2/3-x)TiO₃ (0≤x≤2/3), Li₅La₃Ta₂O₁₂, Li₇La₃Zr₂O₁₂,Li₆BaLa₂Ta₂O₁₂, Li_(3.6)Si_(0.6)P_(0.4)O₄, or the like may be cited.

As the sulfide-based solid electrolyte, it is not limited particularly,and any solid electrolyte may be used as long as it contains a sulfur(S), and also, it is having a lithium ion conductivity and an electroninsulating property. As the sulfide-based solid electrolyte, forexample, Li₂S—P₂S₅, Li₂S—SiS₂, Lil-Li₂S—SiS₂, Lil-Li₂S—P₂S₅,Lil-Li₂S—B₂S₃, Li₃PO₄—Li₂S—SiS, Lil-Li₂S—P₂O₅, Lil-Li₃PO₄—P₂S₅, or thelike may be cited.

In addition, as the inorganic solid electrolyte, a solid electrolyteother than the above solid electrolyte may be used, and for example,Li₃N, Lil, Li₃N-Lil-LiOH, or the like may be used.

As the organic solid electrolyte, it is not limited particularly, aslong as it is a polymer compound having an ion conductivity, and forexample, a polyethylene oxide, a polypropylene oxide, a copolymerthereof, or the like may be used. In addition, the organic solidelectrolyte may comprise the supporting salt (lithium salt).

(e) Structure and Shape of Battery

A lithium ion secondary battery relating to one embodiment of thepresent invention is composed, for example by the positive electrode,the negative electrode, the separator and the non-aqueous electrolyte.In addition, a shape of the lithium ion secondary battery is not limitedparticularly, and it may be formed in various shapes such as acylindrical shape or a layered shape. Even when the lithium ionsecondary battery is adopting any shape, the positive electrode and thenegative electrode are laminated via the separator to form an electrodebody, and the obtained electrode body is impregnated with thenon-aqueous electrolyte, and a positive electrode current collector anda positive electrode terminal communicating to outside, and also, anegative electrode current collector and a negative electrode terminalcommunicating to outside are connected using a current collecting leador the like, and sealed in a battery case to complete the lithium ionsecondary battery.

A lithium ion secondary battery relating to one embodiment of thepresent invention is capable of improving a battery characteristic, andalso, capable of inhibiting an aggregation by sintering and surelydecreasing a sodium content especially, by comprising a positiveelectrode composed of the above positive electrode active material.

EXAMPLES

Next, explaining in detail by examples about a nickel manganese cobaltcomposite hydroxide relating to one embodiment of the present invention,and a method for producing the nickel manganese cobalt compositehydroxide, a lithium nickel manganese cobalt composite oxide, and alithium ion secondary battery. In addition, the present invention is notlimited to these examples.

A transition metal composite hydroxide obtained in a crystallizationprocess described in each of Examples 1 to 13 and Comparative Examples 1to 9 was collected as a nickel manganese cobalt composite hydroxidewhich is a precursor, via a washing, filtering, and drying operation,and then, the nickel manganese cobalt composite hydroxide was subjectedto various analyses by following methods.

[Composition, Calcium and Magnesium Content]

A composition, calcium and magnesium content were analyzed by an aciddecomposition—ICP emission spectrometry, and an ICPE-9000 (manufacturedby SHIMADZU CORPORATION), which is a multiple ICP emission spectrometer,was used for a measurement.

[Sodium and Potassium Content]

A sodium and potassium content were analyzed by an aciddecomposition—atomic absorption spectrometry, and an atomic absorptionspectrometer 240AA (manufactured by Agilent Technologies, Inc.), whichis an atomic absorption spectrometer, was used for a measurement.

[Sulfate Radical Content]

A sulfate radical content was determined by analyzing a total sulfurcontent by an acid decomposition—ICP emission spectrometry, and byconverting this total sulfur content to a sulfate radical (SO₄ ²⁻). Inaddition, an ICPE-9000 (manufactured by SHIMADZU CORPORATION), which isa multiple ICP emission spectrometer, was used for a measurement.

[Chloride Radical Content]

A chloride radical content was analyzed by an X-ray fluorescence (XRF)analysis, by analyzing a sample directly, or by analyzing a chlorideradical contained in a distillation operation by separating a chlorideradical in a form of a silver chloride. In addition, an Axios(manufactured by Spectris Co., Ltd.), which is an X-ray fluorescencespectrometer, was used for a measurement.

[Average Particle Size and Particle Size Distribution]

An average particle size (MV) and a particle size distribution[(d90−d10)/average particle size] were determined from a volume-baseddistribution measured by using a laser diffraction scattering method. Inaddition, a Microtrac MT3300EXII (manufactured by MicrotracBEL Corp.),which is a laser diffraction scattering particle size distributionmeasuring device, was used for a measurement.

[Specific Surface Area]

A specific surface area was analyzed by a nitrogen gas adsorption anddesorption method by a BET one-point method, and a Macsorb 1200 series(manufactured by MOUNTECH Co., Ltd.), which is a specific surface areameasuring device, was used for a measurement.

[Production and Evaluation of Positive Electrode Active Material]

In addition, a lithium metal composite oxide, more concretely, a lithiumnickel manganese cobalt composite oxide, which is a positive electrodeactive material made from the nickel manganese cobalt compositehydroxide of the present invention, was produced and evaluated by afollowing method.

[A. Production of Positive Electrode Active Material]

A nickel manganese cobalt composite hydroxide, which is a precursor, washeat-treated in an air flow (oxygen: 21 vol %) at 700 degrees Celsiusfor 6 hours, and a metal composite oxide was collected. Then, a lithiumhydroxide, which is a lithium compound, was weighed such that a ratio ofLi/Me was 1.025, and was mixed with the collected metal composite oxideto prepare a lithium mixture. In addition, a mixing operation wasperformed by using a shaker mixer (TURBULA TypeT2C manufactured by WillyA Bachofen (WAB)).

Then, the prepared lithium mixture was subjected to a calcination at 500degrees Celsius for 4 hours and then fired at 730 degrees Celsius for 24hours in an oxygen flow (oxygen: 100% by volume), cooled, and thendisintegrated to obtain a lithium nickel manganese cobalt compositeoxide.

[B. Evaluation of Positive Electrode Active Material]

In the obtained lithium nickel manganese cobalt composite oxide, asodium content, a potassium content, a calcium content, a magnesiumcontent, a sulfate radical content, and a chloride radical content wereanalyzed by using the above analysis methods and analysis devices. Inaddition, a Me site occupancy factor, which represents a crystallinityof the lithium nickel manganese cobalt composite oxide, was calculatedby a Rietveld analysis of a diffraction pattern obtained using an X-raydiffractometer (XRD). In addition, an X-ray diffractometer X'Pert PRO(manufactured by Spectris Co. Ltd.) was used for a measurement. A Mesite occupancy factor indicates a presence ratio of metal elements, i.e.a nickel, a manganese, a cobalt and an additive element M in the lithiumnickel manganese cobalt composite oxide, occupied in a metal layer (Mesite) of a layered structure. A Me site occupancy factor is correlatedwith a battery characteristic and it shows an excellent batterycharacteristic as a Me site occupancy factor is higher.

Hereinafter, explaining about each condition of examples and comparativeexamples.

Example 1

In Example 1, 0.9 L of a water was placed in a reaction tank (5 L) of acrystallization in a crystallization process, and a temperature in thereaction tank was set to 40 degrees Celsius while the water in thereaction tank was stirred, and a nitrogen gas was passed through thereaction tank to be a nitrogen atmosphere. An oxygen concentration of aspace in the reaction tank was 2.0% by volume at this time.

Appropriate amounts of a 25% sodium hydroxide aqueous solution and a 25%ammonia water, which is an ammonium ion supplier, were added to thewater in the reaction tank such that a pH of a reaction solution in thereaction tank was adjusted to 12.8 as a pH measured on the basis of aliquid temperature of 25 degrees Celsius. Further, a concentration ofammonium ions in the reaction solution was adjusted to 10 g/L.

Then, nickel sulfate, manganese sulfate, and cobalt chloride weredissolved in a water to prepare a 2.0 mol/L of a raw material solution.The raw material solution was adjusted such that a molar ratio of eachmetal element was Ni:Mn:Co=1:1:1. Further, a sodium hydroxide, which isan alkali metal hydroxide, and a sodium carbonate, which is a carbonate,were dissolved in a water such that [CO₃ ²⁻]/[OH⁻] was 0.025 to preparean alkaline solution.

The raw material solution was added to the reaction solution in thereaction tank at 12.9 mL/min. At the same time, the ammonium ionsupplier and the alkaline solution were also added to the reactionsolution in the reaction tank at constant rates such that a pH of thereaction solution was controlled to be 12.8 (pH in a nucleation process)while a concentration of ammonium ions in the reaction solution wasmaintained at 10 g/L. In this way, a nucleation was performed byperforming a crystallization for 2 minutes 30 seconds.

Then, a 64% sulfuric acid was added until a pH of the reaction solutionhas reached 11.6 (pH in a particle growth process) as a pH measured onthe basis of a liquid temperature of 25 degrees Celsius. Then, after apH of the reaction solution has reached 11.6 as a pH measured on thebasis of a liquid temperature of 25 degrees Celsius, a particle growthwas performed by continuing a crystallization for 4 hours whilecontrolling a pH at 11.6, by supplying the raw material solution, theammonium ion supplier, and the alkaline solution again, to obtain atransition metal composite hydroxide.

After a solid-liquid separation of the obtained transition metalcomposite hydroxide by a filter press filtration device, impurities wereremoved from the transition metal composite hydroxide by passing awashing liquid through the filter press filtration device in aproportion of 5L of the washing liquid with respect to 1 kg of thetransition metal composite hydroxide, by using an ammonium hydrogencarbonate solution with a concentration of 0.05 mol/L as the washingliquid, and then, it was further washed with a water by passing througha water. And, a water adhered to the washed transition metal compositehydroxide was dried to obtain a nickel manganese cobalt compositehydroxide, which is a precursor.

Example 2

In Example 2, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a molar ratio of a nickel,a manganese, and a cobalt in the raw material solution was adjusted suchthat Ni:Mn:Co=6:2:2, when preparing 2.0 mol/L of the raw materialsolution by dissolving a nickel sulfate, a manganese sulfate, and acobalt chloride in a water.

Example 3

In Example 3, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a molar ratio of a nickel,a manganese, and a cobalt in the raw material solution was adjusted suchthat Ni:Mn:Co=2:7:1, when preparing 2.0 mol/L of the raw materialsolution by dissolving a nickel sulfate, a manganese sulfate, and acobalt chloride in a water.

Example 4

In Example 4, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that the alkaline solution wasprepared such that [CO₃ ²⁻]/[OH⁻] was 0.003.

Example 5

In Example 5, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that the alkaline solution wasprepared such that [CO₃ ²⁻]/[OH⁻] was 0.048.

Example 6

In Example 6, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a pH in the nucleationprocess was 13.6.

Example 7

In Example 7, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a pH in the nucleationprocess was 12.3.

Example 8

In Example 8, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a pH in the particlegrowth process was 11.8.

Example 9

In Example 9, a nickel manganese cobalt composite hydroxide was obtainedin a same manner as in Example 1, except that a pH in the particlegrowth process was 10.6.

Example 10

In Example 10, a nickel manganese cobalt composite hydroxide wasobtained in a same manner as in Example 1, except that the alkalinesolution was prepared using a potassium hydroxide as an alkali metalhydroxide and a potassium carbonate as a carbonate.

Example 11

In Example 11, a nickel manganese cobalt composite hydroxide wasobtained in a same manner as in Example 1, except that the alkalinesolution was prepared using an ammonium carbonate as a carbonate, andthat a concentration of ammonium ions was adjusted to 20 g/L.

Example 12

In Example 12, a nickel manganese cobalt composite hydroxide wasobtained in a same manner as in Example 1, except that a temperature inthe reaction tank was set to 35 degrees Celsius.

Example 13

In Example 13, a nickel manganese cobalt composite hydroxide wasobtained in a same manner as in Example 1, except that an ammoniumhydrogen carbonate solution with a concentration of 1.00 mol/L was usedas the washing liquid.

Comparative Example 1

In Comparative Example 1, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that a molar ratioof a nickel, a manganese, and a cobalt in the raw material solution wasadjusted such that Ni:Mn:Co=2:6:2, when preparing 2.0 mol/L of the rawmaterial solution by dissolving a nickel sulfate, a manganese sulfate,and a cobalt chloride in a water, and that the alkaline solution wasprepared such that [CO₃ ²⁻]/[OH⁻] was 0.001.

Comparative Example 2

In Comparative Example 2, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that the alkalinesolution was prepared using only a sodium hydroxide, and that [CO₃²⁻]/[OH⁻] was not considered.

Comparative Example 3

In Comparative Example 3, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that the alkalinesolution was prepared such that [CO₃ ²⁻]/[OH⁻] was 0.001.

Comparative Example 4

In Comparative Example 4, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that the alkalinesolution was prepared such that [CO₃ ²⁻]/[OH⁻] was 0.055.

Comparative Example 5

In Comparative Example 5, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that the washingprocess was omitted so that a washing by an ammonium hydrogen carbonatesolution was not performed.

Comparative Example 6

In Comparative Example 6, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that an ammoniumhydrogen carbonate solution with a concentration of 0.02 mol/L was usedas the washing liquid.

Comparative Example 7

In Comparative Example 7, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that an ammoniumcarbonate solution was used as the washing liquid.

Comparative Example 8

In Comparative Example 8, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that a sodiumhydrogen carbonate solution was used as the washing liquid.

Comparative Example 9

In Comparative Example 9, a nickel manganese cobalt composite hydroxidewas obtained in a same manner as in Example 1, except that a sodiumcarbonate solution was used as the washing liquid.

The above conditions and results are indicated in Table 1, Table 2, andTable 3.

TABLE 1 Nickel manganese cobalt composite hydroxide (precursor)Crystallization process [CO₃ ²⁻]/ Nucleation Particle Alkali metalNi:Mn:Co [OH⁻] pH growth pH hydroxide Carbonate Example 1 1:1:1 0.02512.8 11.6 Sodium hydroxide Sodium carbonate Example 2 6:2:2 0.025 12.811.6 Sodium hydroxide Sodium carbonate Example 3 2:7:1 0.025 12.8 11.6Sodium hydroxide Sodium carbonate Example 4 1:1:1 0.003 12.8 11.6 Sodiumhydroxide Sodium carbonate Example 5 1:1:1 0.048 12.8 11.6 Sodiumhydroxide Sodium carbonate Example 6 1:1:1 0.025 13.6 11.6 Sodiumhydroxide Sodium carbonate Example 7 1:1:1 0.025 12.3 11.6 Sodiumhydroxide Sodium carbonate Example 8 1:1:1 0.025 12.8 11.8 Sodiumhydroxide Sodium carbonate Example 9 1:1:1 0.025 12.8 10.6 Sodiumhydroxide Sodium carbonate Example 10 1:1:1 0.025 12.8 11.6 Potassiumhydroxide Potassium carbonate Example 11 1:1:1 0.025 12.8 11.6 Sodiumhydroxide Ammonium carbonate Example 12 1:1:1 0.025 12.8 11.6 Sodiumhydroxide Sodium carbonate Example 13 1:1:1 0.025 12.8 11.6 Sodiumhydroxide Sodium carbonate Comparative 2:6:2 0.001 12.8 11.6 Sodiumhydroxide Sodium carbonate example 1 Comparative 1:1:1 — 12.8 11.6Sodium hydroxide — example 2 Comparative 1:1:1 0.001 12.8 11.6 Sodiumhydroxide Sodium carbonate example 3 Comparative 1:1:1 0.055 12.8 11.6Sodium hydroxide Sodium carbonate example 4 Comparative 1:1:1 0.025 12.811.6 Sodium hydroxide Sodium carbonate example 5 Comparative 1:1:1 0.02512.8 11.6 Sodium hydroxide Sodium carbonate example 6 Comparative 1:1:10.025 12.8 11.6 Sodium hydroxide Sodium carbonate example 7 Comparative1:1:1 0.025 12.8 11.6 Sodium hydroxide Sodium carbonate example 8Comparative 1:1:1 0.025 12.8 11.6 Sodium hydroxide Sodium carbonateexample 9 Nickel manganese cobalt composite hydroxide (precursor)Crystallization process Washing process Ammonium ion ReactionConcentration concentration temperature of washing liquid (g/L) (° C.)Type of washing liquid (mol/L) Example 1 10 40 Ammonium hydrogencarbonate 0.05 Example 2 10 40 Ammonium hydrogen carbonate 0.05 Example3 10 40 Ammonium hydrogen carbonate 0.05 Example 4 10 40 Ammoniumhydrogen carbonate 0.05 Example 5 10 40 Ammonium hydrogen carbonate 0.05Example 6 10 40 Ammonium hydrogen carbonate 0.05 Example 7 10 40Ammonium hydrogen carbonate 0.05 Example 8 10 40 Ammonium hydrogencarbonate 0.05 Example 9 10 40 Ammonium hydrogen carbonate 0.05 Example10 10 40 Ammonium hydrogen carbonate 0.05 Example 11 20 40 Ammoniumhydrogen carbonate 0.05 Example 12 10 35 Ammonium hydrogen carbonate0.05 Example 13 10 40 Ammonium hydrogen carbonate 1.00 Comparative 10 40Ammonium hydrogen carbonate 0.05 example 1 Comparative 10 40 Ammoniumhydrogen carbonate 0.05 example 2 Comparative 10 40 Ammonium hydrogencarbonate 0.05 example 3 Comparative 10 40 Ammonium hydrogen carbonate0.05 example 4 Comparative 10 40 — — example 5 Comparative 10 40Ammonium hydrogen carbonate 0.02 example 6 Comparative 10 40 Ammoniumcarbonate 0.05 example 7 Comparative 10 40 Sodium hydrogen carbonate0.05 example 8 Comparative 10 40 Sodium carbonate 0.05 example 9

TABLE 2 Nickel manganese cobalt composite hydroxide (precursor) (d90 −d10)/ Sulphate Chloride Average average Specific Sodium PotassiumCalcium Magnesium radical radical particle size particle size surfacearea (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% bymass) MV (μm) MV (m²/g) Example 1 <0.0005 <0.0005 <0.0005 <0.0005 0.160.005 7.1 0.50 14 Example 2 <0.0005 <0.0005 <0.0005 <0.0005 0.17 0.0067.1 0.48 13 Example 3 <0.0005 <0.0005 <0.0005 <0.0005 0.16 0.005 7.20.49 13 Example 4 <0.0005 <0.0005 <0.0005 <0.0005 0.19 0.008 6.9 0.54 12Example 5 <0.0005 <0.0005 <0.0005 <0.0005 0.19 0.008 6.8 0.53 11 Example6 <0.0005 <0.0005 <0.0005 <0.0005 0.18 0.007 7.3 0.50 16 Example 7<0.0005 <0.0005 <0.0005 <0.0005 0.18 0.007 7.1 0.48 17 Example 8 <0.0005<0.0005 <0.0005 <0.0005 0.18 0.007 6.9 0.47 15 Example 9 <0.0005 <0.0005<0.0005 <0.0005 0.18 0.007 6.9 0.49 14 Example 10 <0.0005 <0.0005<0.0005 <0.0005 0.17 0.006 7.0 0.48 15 Example 11 <0.0005 <0.0005<0.0005 <0.0005 0.17 0.006 6.8 0.51 17 Example 12 <0.0005 <0.0005<0.0005 <0.0005 0.17 0.006 7.4 0.49 16 Example 13 <0.0005 <0.0005<0.0005 <0.0005 0.17 0.006 7.0 0.50 14 Comparative 0.0007 <0.0005<0.0005 <0.0005 0.26 0.014 6.8 0.57 17 example 1 Comparative 0.0012<0.0005 <0.0005 <0.0005 0.28 0.015 7.3 0.57 18 example 2 Comparative0.0009 <0.0005 <0.0005 <0.0005 0.28 0.014 7.0 0.57 15 example 3Comparative 0.0010 <0.0005 <0.0005 <0.0005 0.27 0.015 7.4 0.59 15example 4 Comparative 0.2800 <0.0005 <0.0005 <0.0005 0.38 0.140 6.8 0.5213 example 5 Comparative 0.0006 <0.0005 <0.0005 <0.0005 0.22 0.011 7.00.51 14 example 6 Comparative 0.0016 <0.0005 <0.0005 <0.0005 0.21 0.0116.9 0.50 14 example 7 Comparative 0.0220 0.0008 0.0022 0.0009 0.25 0.0157.0 0.49 14 example 8 Comparative 0.0370 0.0013 0.0023 0.0011 0.27 0.0147.1 0.49 13 example 9

TABLE 3 Lithium nickel manganese cobalt composite oxide (positiveelectrode active material) Sulphate Chloride Average Aggregation Me siteSodium Potassium Calcium Magnesium radical radical particle size MV ofsecondary occupancy (% by mass) (% by mass) (% by mass) (% by mass) (%by mass) (% by mass) MV (μm) ratio particles (%) factor (%) Example 1<0.0005 <0.0005 <0.0005 <0.0005 0.10 0.001 7.0 0.99 3 93.3 Example 2<0.0005 <0.0005 <0.0005 <0.0005 0.11 0.001 7.1 1.00 3 93.4 Example 3<0.0005 <0.0005 <0.0005 <0.0005 0.12 0.001 7.1 0.99 3 93.3 Example 4<0.0005 <0.0005 <0.0005 <0.0005 0.15 0.003 6.8 0.99 3 93.1 Example 5<0.0005 <0.0005 <0.0005 <0.0005 0.15 0.003 6.9 1.01 4 93.1 Example 6<0.0005 <0.0005 <0.0005 <0.0005 0.14 0.002 7.2 0.99 3 93.2 Example 7<0.0005 <0.0005 <0.0005 <0.0005 0.14 0.003 7.1 1.00 3 93.3 Example 8<0.0005 <0.0005 <0.0005 <0.0005 0.13 0.002 6.7 0.97 2 93.1 Example 9<0.0005 <0.0005 <0.0005 <0.0005 0.14 0.003 7.0 1.01 4 93.2 Example 10<0.0005 <0.0005 <0.0005 <0.0005 0.12 0.002 7.2 1.03 4 93.2 Example 11<0.0005 <0.0005 <0.0005 <0.0005 0.14 0.002 6.9 1.01 4 93.3 Example 12<0.0005 <0.0005 <0.0005 <0.0005 0.15 0.002 7.3 0.99 3 93.1 Example 13<0.0005 <0.0005 <0.0005 <0.0005 0.12 0.001 6.9 0.99 3 93.3 Comparative0.0011 <0.0005 <0.0005 <0.0005 0.21 0.008 7.2 1.06 7 89.8 example 1Comparative 0.0012 <0.0005 <0.0005 <0.0005 0.21 0.009 7.8 1.07 7 89.5example 2 Comparative 0.0010 <0.0005 <0.0005 <0.0005 0.21 0.009 7.4 1.066 89.7 example 3 Comparative 0.0011 <0.0005 <0.0005 <0.0005 0.22 0.0087.9 1.07 7 88.9 example 4 Comparative 0.2900 <0.0005 <0.0005 <0.00050.27 0.048 7.4 1.09 9 92.8 example 5 Comparative 0.0006 <0.0005 <0.0005<0.0005 0.11 0.007 7.4 1.06 6 92.2 example 6 Comparative 0.0014 <0.0005<0.0005 <0.0005 0.11 0.006 7.4 1.07 7 91.5 example 7 Comparative 0.02000.0008 0.0013 0.0010 0.12 0.010 7.5 1.07 7 91.8 example 8 Comparative0.0330 0.0010 0.0016 0.0011 0.12 0.009 7.6 1.07 7 92.6 example 9

(Comprehensive Evaluation)

As indicated in Table 1, Table 2, and Table 3, in the nickel manganesecobalt composite hydroxide, which is a precursor, of Examples 1 to 13,all conditions of the crystallization process and the washing processwere all in a preferable range. Therefore, not only the nickel manganesecobalt composite hydroxide, but also in the lithium nickel manganesecobalt composite oxide, which is a positive electrode active material,with respect to a removal of impurities, a potassium content, a calciumcontent, and a magnesium content, in addition to a sulfate radicalcontent and a chloride radical content, including a sodium content, weredecreased sufficiently. Further, in the lithium nickel manganese cobaltcomposite oxide, a Me site occupancy factor was more than 93.0%, andalso resulted as excellent in a crystallinity, and a batterycharacteristic was improved.

Especially, regarding a sodium content, both of the precursor and thepositive electrode active material showed an extremely excellent resultsthat a data of all examples were less than a quantitative (analysis)lower limit (0.0005% by mass). In addition, also regarding a potassium,a calcium, and a magnesium, similar results as a sodium were obtained.Therefore, in the positive electrode active material, a sodium or thelike were not solid-solving in a lithium site, and a MV ratio, which isan index of an aggregation by sintering, was in a range of 0.95 to 1.05,and further, when observing 100 or more particles selected randomly by ascanning electron microscope, a number that an aggregation of secondaryparticles is observed was 5% or less with respect to a total number ofobserved secondary particles.

Here, a quantitative lower limit means a minimum quantity or a minimumconcentration capable of an analysis (quantitation) of a targetcomponent by a certain analysis method. In addition, a minimum amount(value) capable of a signal detection of a target component in ameasurement is called a detection limit, and a minimum amount (value) tosecure a reliability in a signal of a target component obtained by ameasurement is called a measurement lower limit. Further, in a processof preparing an analysis sample into a measurement specimen liquid, aquantitative lower limit is determined by multiplying a measurementlower limit by a dilution magnification indicating how much condensed ordiluted from the original analysis sample.

In other words, for example, in a sodium content and a potassium contentof the present invention, 100 mL of a measurement specimen liquid wasprepared (dilution magnification is 100 times) by acid-decomposing 1 gof an analysis sample with respect to a measurement lower limit 0.05μg/mL of an atomic absorption spectrometer, so a quantitative lowerlimit is 5 ppm (μg/g), i.e. 0.0005% by mass. In addition, in a calciumcontent and a magnesium content of the present invention, 100 mL of ameasurement specimen liquid was prepared (dilution magnification is 100times) by acid-decomposing 1 g of an analysis sample with respect to ameasurement lower limit 0.05 μg/mL of an ICP emission spectrometer, so aquantitative lower limit is 5 ppm (μg/g), i.e. 0.0005% by mass.

On the other hand, in Comparative Examples 1 to 9, [CO₃ ²⁻]/[OH⁻] whenpreparing the alkaline solution, or a concentration of the ammoniumhydrogen carbonate solution, which is the washing liquid, were not in apreferable range, or a washing liquid other than the ammonium hydrogencarbonate solution was used, and it was deviated from optimumconditions, so an excellent effect like the examples were not obtained.

From the above, it is possible to provide a nickel manganese cobaltcomposite hydroxide, which is a precursor of a positive electrode activematerial of a lithium ion secondary battery capable of improving abattery characteristic, and also, capable of surely decreasing a sodiumcontent especially, a method for producing the nickel manganese cobaltcomposite hydroxide, a lithium nickel manganese cobalt composite oxide,and a lithium ion secondary battery. In addition, it is possible toprovide a lithium nickel manganese cobalt composite oxide, which is apositive electrode active material inhibiting an aggregation bysintering, manufactured by using the nickel manganese cobalt compositehydroxide in which a sodium content is surely decreased, and a lithiumion secondary battery.

By the way, for example, in a field of analytical chemistry, a reagentmanufacturer providing a standard substance to be a standard of ananalysis and a test is working on a further high purification of thestandard substance every day, and a research for decreasing impuritiesto the utmost have been conducted. For this reason, it is obvious thatthe lithium nickel manganese cobalt composite oxide, in which a contentof impurities including a sodium is decreased as possible, is not amatter only changing a designing matter.

In addition, it was explained in detail about each embodiment and eachexample of the present invention as the above, but it is easy for thosewho skilled in the art to understand that various modifications arepossible without substantially departing from new matters and effects ofthe present invention. Therefore, all of such modified examples areincluded within the scope of the present invention.

For example, a term used at least once in the description or drawingstogether with a different term that is broader or the same in meaningcan also be replaced by the different term in any place in thedescription or drawings. Further, the operations and the configurationsof the nickel manganese cobalt composite hydroxide, the method forproducing the nickel manganese cobalt composite hydroxide, the lithiumnickel manganese cobalt composite oxide, and the lithium ion secondarybattery are not limited to those described in each embodiment and eachexample of the present invention, but may be carried out in variousmodifications.

GLOSSARY OF DRAWING REFERENCES

-   S10 Crystallization process-   S11 Nucleation process-   S12 Particle growth process-   S20 Washing process

1. A nickel manganese cobalt composite hydroxide, which is a precursorof a positive electrode active material, and which is composed ofsecondary particles to which primary particles containing a nickel, amanganese, and a cobalt are aggregated, or composed of the primaryparticles and the secondary particles, wherein a sodium contentcontained in the nickel manganese cobalt composite hydroxide is lessthan 0.0005% by mass.
 2. The nickel manganese cobalt composite hydroxideaccording to claim 1, wherein a specific surface area of the nickelmanganese cobalt composite hydroxide is 10 to 20 m²/g.
 3. The nickelmanganese cobalt composite hydroxide according to claim 1, wherein asulfate radical content contained in the nickel manganese cobaltcomposite hydroxide is 0.2% by mass or less, and also, a chlorideradical content is 0.01% by mass or less.
 4. The nickel manganese cobaltcomposite hydroxide according to claim 1, wherein a value of[(d90−d10)/average particle size], which is an index indicating a spreadof a particle size distribution of the nickel manganese cobalt compositehydroxide, is 0.55 or less.
 5. The nickel manganese cobalt compositehydroxide according to claim 1, wherein the nickel manganese cobaltcomposite hydroxide is represented by a general formula:Ni_(x)Co_(y)Mn_(z)M_(t)(OH)_(2+a) wherein x+y+z+t=1, 0.20≤x≤0.80,0.10≤y≤0.50, 0.10≤z≤0.90, 0≤t≤0.10, 0≤a≤0.5, and M is at least oneselected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W.
 6. The nickelmanganese cobalt composite hydroxide according to claim 1, wherein acontent of at least one of a potassium, a calcium, and a magnesiumcontained in the nickel manganese cobalt composite hydroxide is lessthan 0.0005% by mass.
 7. A method for producing a nickel manganesecobalt composite hydroxide, which is a precursor of a positive electrodeactive material, and which is composed of secondary particles to whichprimary particles containing a nickel, a manganese, and a cobalt areaggregated, or composed of the primary particles and the secondaryparticles, comprising: a crystallization process for obtaining atransition metal composite hydroxide by crystallizing in a reactionsolution obtained by adding a raw material solution containing a nickel,a manganese, and a cobalt, a solution containing an ammonium ionsupplier, and an alkaline solution; and a washing process for washingthe transition metal composite hydroxide obtained in the crystallizationprocess by a washing liquid, wherein the alkaline solution in thecrystallization process is a mixed solution of an alkali metal hydroxideand a carbonate, a ratio [CO₃ ²⁻]/[OH⁻] of the carbonate with respect tothe alkali metal hydroxide in the mixed solution is 0.002 to 0.050, acrystallization is performed in a non-oxidizing atmosphere in thecrystallization process, and the washing liquid in the washing processis an ammonium hydrogen carbonate solution with a concentration of 0.05mol/L or more.
 8. The method for producing the nickel manganese cobaltcomposite hydroxide according to claim 7, wherein the crystallizationprocess further comprises a nucleation process and a particle growthprocess, and in the nucleation process, a nucleation is performed byadding the alkaline solution to the reaction solution such that a pHmeasured on the basis of a liquid temperature of 25 degrees Celsius willbe 12.0 to 14.0, and in the particle growth process, the alkalinesolution is added to the reaction solution containing nuclei formed inthe nucleation process such that a pH measured on the basis of a liquidtemperature of 25 degrees Celsius will be 10.5 to 12.0.
 9. The methodfor producing the nickel manganese cobalt composite hydroxide accordingto claim 7, wherein the nickel manganese cobalt composite hydroxideobtained via the washing process is a nickel manganese cobalt compositehydroxide, which is a precursor of a positive electrode active material,and which is composed of secondary particles to which primary particlescontaining a nickel, a manganese, and a cobalt are aggregated, orcomposed of the primary particles and the secondary particles, and asodium content contained in the nickel manganese cobalt compositehydroxide is less than 0.0005% by mass.
 10. A lithium nickel manganesecobalt composite oxide composed of secondary particles to which primaryparticles containing a lithium, a nickel, a manganese, and a cobalt areaggregated, or composed of the primary particles and the secondaryparticles, wherein a sodium content contained in the lithium nickelmanganese cobalt composite oxide is less than 0.0005% by mass.
 11. Thelithium nickel manganese cobalt composite oxide according to claim 10,wherein a sulfate radical content contained in the lithium nickelmanganese cobalt composite oxide is 0.15% by mass or less, and achloride radical content is 0.005% by mass or less, and also, a Me siteoccupancy factor is 93.0% or more.
 12. The lithium nickel manganesecobalt composite oxide according to claim 10, wherein a ratio of anaverage particle size of the lithium nickel manganese cobalt compositeoxide divided by an average particle size of a nickel manganese cobaltcomposite hydroxide, which is a precursor, is 0.95 to 1.05.
 13. Thelithium nickel manganese cobalt composite oxide according to claim 10,wherein, when observing 100 or more particles of the lithium nickelmanganese cobalt composite oxide selected randomly by a scanningelectron microscope, a number that an aggregation of secondary particlesis observed is 5% or less with respect to a total number of observedsecondary particles.
 14. The lithium nickel manganese cobalt compositeoxide according to claim 10, wherein a content of at least one of apotassium, a calcium, and a magnesium contained in the lithium nickelmanganese cobalt composite oxide is less than 0.0005% by mass.
 15. Alithium ion secondary battery comprising a positive electrode at leastcontaining the lithium nickel manganese cobalt composite oxide accordingto claim 10.